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European Journal of Applied Sciences – Vol. 12, No. 2

Publication Date: April 25, 2024

DOI:10.14738/aivp.122.16797

Assem, H. D., Donkor, M. E. K., Tamakloe, R. Y., & Nkum, R. K. (2024). A Review of UV-Vis on Polymers; Polyaniline (PANI) and Its

Nanocomposites. European Journal of Applied Sciences, Vol - 12(2). 322-346.

Services for Science and Education – United Kingdom

A Review of UV-Vis on Polymers; Polyaniline (PANI) and Its

Nanocomposites

Humphrey Darkeh Assem

Department of Physics Kwame Nkrumah University

Science and Technology Kumasi-Ghana (West Africa)

Michael Edem Kweku Donkor

Department of Physics Kwame Nkrumah University

Science and Technology Kumasi-Ghana (West Africa)

Reuben Yao Tamakloe

Department of Physics Kwame Nkrumah University

Science and Technology Kumasi-Ghana (West Africa)

Robert K. Nkum

Department of Physics Kwame Nkrumah University

Science and Technology Kumasi-Ghana (West Africa)

ABSTRACT

In recent years, the utilization of Polyaniline (PANI) and its nano-composites has

garnered considerable attention across diverse domains encompassing electronics,

sensing technologies, and energy storage applications due to their multifaceted

utility. Central to the investigation of their properties is UV-Vis spectroscopy, which

has emerged as an indispensable analytical tool. This review aims to shed light on

recent advancements in UV-Vis spectroscopic techniques as applied to PANI films

and their corresponding nano-composites. The discourse begins by explaining the

fundamental principles of UV-Vis spectroscopy and its relevance in examining the

electronic transitions within PANI and its nano-composites. Subsequently, the

synthetic methodologies employed for fabricating PANI films and nano-composites

are expounded upon, with particular emphasis on discerning the influence of

various parameters on their optical attributes. Furthermore, the implications of

dopants, oxidants, and nano structural configurations on the UV-Vis spectra of PANI

are meticulously examined. Additionally, this review delves into the applications of

UV-Vis spectroscopy in shedding more light on the structural and optical attributes

of PANI-based materials tailored for specific functions such as chemical sensing,

optoelectronics, and energy storage systems. Recent advancements in the

development of innovative PANI nano-composites endowed with augmented

optical properties are scrutinized, highlighting their potential utility across a

spectrum of technological domains. Moreover, the challenges and prospective

avenues in harnessing UV-Vis spectroscopy for the characterization of PANI films

and nano-composites are deliberated upon, with strategies proposed to overcome

limitations including spectral superposition, sample preparation intricacies, and

the interpretation of complex spectra. Furthermore, prospective directions for

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Assem, H. D., Donkor, M. E. K., Tamakloe, R. Y., & Nkum, R. K. (2024). A Review of UV-Vis on Polymers; Polyaniline (PANI) and Its Nanocomposites.

European Journal of Applied Sciences, Vol - 12(2). 322-346.

URL: http://dx.doi.org/10.14738/aivp.122.16797

further research endeavours aimed at leveraging the full potential of UV-Vis

spectroscopy in enhancing the comprehension and application scope of PANI-based

materials are mapped out.

Keywords: Polyaniline (PANI), Nano-composites, UV-Vis spectroscopy, Spectroscopic

techniques, Electronic transitions, Synthetic methodologies, Optical attributes, Dopants,

Oxidants, Nano structural configurations, Structural attributes, Chemical sensing,

Optoelectronics

HIGHLIGHTS

1. Polyaniline (PANI) and its nanocomposites exhibit versatility in applications spanning

electronics, sensing technologies, and energy storage, underscoring their broad utility

across diverse domains.

2. UV-VIS spectroscopy emerges as a pivotal analytical tool for scrutinizing the optical

properties of PANI films, offering indispensable insights into their optical

characteristics.

3. The fabrication techniques employed significantly impact the optical properties of PANI

films and nanocomposites, highlighting the importance of method selection in tailoring

their optical performance.

4. UV-VIS spectroscopy plays a crucial role in the comprehensive characterization of PANI

materials, enabling a nuanced understanding essential for their effective utilization

across varied applications.

5. Addressing challenges inherent in UV-Vis spectroscopy stands to enrich the

understanding and application scope of PANI materials, necessitating the development

of strategies to mitigate issues such as spectral superposition and complexities in

sample preparation and interpretation.

INTRODUCTION

Polyaniline (PANI) has garnered significant attention across various disciplines due to its

diverse electrical, optical, and chemical properties (Beygisangchin et al., 2024; Banerjee, 2019).

The application of PANI thin films and nano-composites in fields such as sensors, optoelectronic

devices, and energy storage systems underscores the necessity of comprehending their optical

behavior for improved functionality. UV-Vis spectroscopy emerges as a crucial analytical

method for investigating these materials, providing deep insights into their electronic structure

and interactions. PANI, as a member of conducting polymers, presents intriguing features

stemming from the delocalization of π-electrons along its backbone, which can be manipulated

through chemical doping or structural modifications (Ibanez et al. 2018). The fabrication of

PANI thin films through techniques like spin-coating, dip-coating, or electrochemical

deposition offers controlled environments for property exploration. UV-Vis spectroscopy,

rooted in ultraviolet and visible light absorption, serves as a valuable tool for unraveling

electronic transitions within PANI thin films, including π-π* transitions and charge transfer

interactions. Analyzing absorption spectra aids in identifying characteristic peaks, facilitating

deductions about structural and electronic alterations. Moreover, this academic review seeks

to extensively explore UV-Vis spectroscopy, including its basic principles, complexities in

instrumentation, wide-ranging applications, and inherent limitations, supported by relevant

scholarly sources. The underlying principle of UV-Vis spectroscopy lies in the interaction

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between matter and ultraviolet and visible light, resulting in electronic transitions and

distinctive spectra, based on the energy disparity between ground and excited states (Förster,

2004; Penner, 2017). Moreover, nano-composites incorporating PANI exhibit enhanced

properties compared to pristine polymer films, with UV-Vis characterization enabling the

exploration of interactions between the polymer matrix and nanofillers, alongside the

assessment of nanofiller morphology and concentration effects on optical properties.

Applications

UV-Vis spectroscopy finds applications in quantitative analysis, qualitative analysis, structural

analysis, kinetic studies, DNA and protein analysis, and environmental monitoring (Harris,

2010; Pan et al., 2017). One common application is the determination of substance

concentration using the Beer-Lambert law,

A = εlc − − − − − − − − − − − (17)

where absorbance (A) is proportional to the molar absorptivity coefficient (ε), path length (b),

and concentration (c). The technique is versatile, allowing the analysis of liquids, solids, and

gases. UV−Vis−NIR spectrometer is able to monitor absorbance, A or transmittance, T in UV –

Vis wavelength range. The relation between incident light of intensity, I and transmitted light

of intensity I0 and Transmittance, T is given by:

T =

I

I0

− − − − − − − − − (18)

and transmission rate is given by:

(T%) = (

I

I0

)100%

Absorbance, A is the inverse of transmittance, T and given by log 1

T

= log I0

I

Thus,

A = −logT = εlc − − − − − − − − − − − (19)

While absorbance displays a proportionality with sample concentration according to Beer's law

and the optical path, transmittance is independent of sample concentration. Additionally, when

the optical path is 1 cm and the concentration of the target substance is 1 mol/l, the

phenomenon is referred to as molar absorption (Tolbin et al., 2017). Molar absorption

coefficient is a property of the substance that is typical under certain circumstances. The

spectrometer can then be used to capture the UV-Vis spectrum.

UV-VIS SPECTROSCOPY IN MOLECULAR ANALYSIS

UV-Visible (UV-Vis) spectroscopy holds paramount significance in molecular analysis by

concentrating on the intricate interplay between electromagnetic fields and matter. This

analytical technique employs ultraviolet and visible light, inducing diverse electronic

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2015). It is paramount that these calibration solutions be meticulously prepared using digital

pipettes and volumetric flasks instead of less precise implements like graduated cylinders and

beakers. Additionally, the calibration solutions should be evenly spaced apart to ensure a

robust calibration curve.

Limitations

While UV-Vis spectroscopy finds extensive utility, it is not without inherent limitations. The

technique offers constrained insights into particular functional groups, and the presence of

absorbing species from external sources can introduce inaccuracies in the obtained results.

Inadequate sensitivity may pose challenges in detecting low concentrations, and the

opaqueness of certain samples may necessitate the application of specialized analytical

methods (Hanson, 1995).

UV-Vis-NIR Spectrophotometer

The UV-Vis-NIR spectrophotometer is designed for the measurement of light absorbance or

transmittance across the ultraviolet-visible (UV-Vis) wavelength range in a given medium. It

encompasses essential components including UV and visible light sources, such as deuterium

or hydrogen lamps and tungsten/halogen lamps respectively, alongside a monochromator,

sample holder in the form of cuvettes, a detector, and a display interface. This instrumentation

facilitates the examination of samples in various states, thereby furnishing invaluable data for

a comprehensive UV-Vis spectrum as depicted in Figure 1. Upon exposure to incident light, an

object experiences fundamental optical phenomena such as absorption, reflection, or

transmission. The spectrophotometer serves as a pivotal tool for quantifying the extent of light

absorption within the UV and Vis spectra. It gauges the intensity of light transmitted through

the sample, contrasting it against a baseline measurement derived from the incident light

source. Through the application of the Beer-Lambert Law, which delineates a direct correlation

between the concentration of a substance in a sample, the path length traversed by light, and

the resultant light absorption, the spectrophotometer is proficient in determining the

concentration of specific analytes present within the sample (Purcell, 2013).

Figure 1: UV-Vis spectrum